Plate evaporator for removing volatiles from liquids

ABSTRACT

A plate assembly for improved removal of volatiles from a flowable material. The assembly includes one or more sets of port-type heat exchanger plates arranged in succession to provide a confined tortuous path of increased capacity for a high velocity flow of the volatiles-containing material. Variation of the gasketing of the plates, so as to include in the tortuous path the optimum number and combination of plate ports, provides increased capacity, while affording control of flow conditions within the assembly in correspondence with the sensitivities of the flowable material. One form of the assembly may constitute a plate contactor for effecting two-phase stripping of volatiles from the flowable material. Another possible form may be a plate evaporator for enhancing evaporative removal of the volatiles.

United States Patent 1 Gebauer [451 Sept. 18,1973

[73] Assignee: Parkson Corporation, Ft.

Lauderdale, Fla.

[22] Filed: June 15, 1970 [21] Appl. No.: 46,283

[52] U.S. Cl. 159/13 R, 159/28 P, 165/167 [51] Int. Cl 801d l/22, B0ld 1/00, F28f 3/08 [58] Field of Search 159/28 R, 28 P;

[56] I References Cited UNITED STATES PATENTS 2,229,306 1/1941 Prestage.... 165/167 2,314,966 3/1943 Astle 165/167 2,428,880 10/1947 Kintner 165/167 3,150,028 9/1964 Wennerberg.... 159/28 P 2,937,856 5/1960 Thomson 165/167 X 2,960,160 11/1960 Goodman..... 159/28 R X 3,073,380 1/1963 Palmason 165/167 X 3,155,565 11/1964 Goodman 159/28 R X 3,399,708 9/1968 Usher et al 159/28 R 3,469,615 9/1969 Usher 159/28 R 9/1969 Palmason 159/28 R FOREIGN PATENTS OR APPLICATIONS 958,699 3/1950 France.... ..165/167 834,829 12/1938 France ..165/167 Primary Examiner-Norman Yudkoff Assistant ExaminerJ. Sofer Attorney-Brumbaugh, Graves, Raymond Donohue and [57] ABSTRACT A plate assembly for improved removal of volatiles from a flowable material. The assembly includes one or more sets of port-type heat exchanger plates arranged in succession to provide a confined tortuous path of increased capacity for a high velocity flow of the volatiles-containing material. Variation of the gasketing of the plates, so as to include in the tortuous path the optimum number and combination of plate ports, provides increased capacity, while affording control of flow conditions within the assembly in correspondence with the sensitivities of the flowable material. One form of the assembly may constitute a plate contactor for effecting two-phase stripping of volatiles from the flowable ma-' terial. Another possible form may be a plate evaporator for enhancing evaporative removal of the volatiles.

, 10 Claims, 9 Drawing Figures Patented Sept. 18, 1973 3,759,308

3 Sheets-Sheet 1 l Stripping -To Condenser VaporInIef IO N, 32

28 1 I F/G.

FIG. 5

INVENTOR. ADAM GEORGE GEBAUER his ATT RNE'YS Material Residue Patented Sept. 18, 1973 3 Sheets-Sheet 2 moZEEmw 9 7 3.522 HFEEB Qz mo SGmPZw now mm A \JJAJA J lmfi E u AKAK INVENTOR.

ADAM GEORGE GEBAUER BY fi nu b 6W4, $011444: 1 J "W" his ATTORNEYS Patented Sept. 18, 1973 3,759,308

3 Sheets-Sheet 5 PLATE EVAPORATOR FOR REMOVING VOLATILES FROM LIQUIDS BACKGROUND OF THE INVENTION This invention relates generally to the removal of volatiles from flowable materials by passing the volatilescontaining material through a plate assembly defining a confined, tortuous flow path and, in particular, to a novel plate assembly that provides a tortuous flow path of increased capacity and improved flow characteristics and that affords selective variation of the porting of the plates so as to allow control of flow pressures and velocities along the tortuous path. More specifically, these advantages are obtained in a plate assembly constructed of liquid-liquid heat exchanger plates of conventional port-type design through varying the gasketing of the plates to include in the flow path the optimum number and combination of plate ports for the particular flowable material to be treated.

Various types of equipments and techniques have been developed to promote the removal of volatiles from flowable materials, including as one form stripping of the volatiles from the material by contacting (under controlled conditions) the material with a vapor having an affinity for the volatile substance. Examples of equipments and techniques, together with a general description of the factors obtaining, both in the nature of operational difficulties and theoretical objectives, for accomplishing efficient stripping of volatile substances are set forth in detail at lines 44 to 72 of column 1 and lines 1 to 59 of column 2 of U.S. Pat. No. 3,469,617, issued on Sept. 30, 1969, to the assignee of the present application. To avoid redundancy, this descriptive subject matter is incorporated by reference into this application in the way of background material.

The foregoing US. Pat. No. 3,469,617, in addition, describes and claims a process for the two-phase stripping of volatile substances from flowable materials that affords significant and important advantages over previously known stripping techniques. In brief, the process includes the steps of injecting a flowable material, in either liquid or solid form, containing a volatile substance to be removed into a high velocity stream of stripping gas so as to form a turbulent admixture of the gas as a continuous phase with discrete particles of the material dispersed therein, passing the admixture through a confined, tortuous path under controlled conditions of temperature, pressure, and velocity such that substantial volatilization, and hence stripping, of the volatile substance is effected within the tortuous path without degradation of the quality of the material being stripped, and exiting the resultant admixture of stripped material and volatiles-containing gas to a separator for separation of the gas and volatiles from the stripped material residue. Suitable apparatus for carrying out the process is also disclosed, including, among other components, a plate pack stripping unit, or contactor, that defines the confined, tortuous path in which stripping of the volatiles from the flowable material is carried out.

An exemplary construction of the plate contactor is illustrated in FIGS. 2 and 4 of the patent. As shown, a multiplicity of port-type heat exchanger plates of conventional liquid-liquid design are spaced apart by gaskets that are arranged to provide, with the plates, a number of narrow spaces or passageways for passage of the continuous gas or vapor phase containing particles of the flowable material. Although such plates typically have from four to six ports, two or three at each end, the gaskets of the contactor are arranged to include only a single port at each end of the plates in communication with the adjacent elongate passageway. Thus each of the plates has one inlet port through which the admixture of the flowable material and stripping vapor flows into the adjacent passageway and one outlet port through which the admixture is exited from the passageway, with the inlet and outlet ports being diagonally positioned at opposite ends of the plate. The inlet ports of the plates are coaxially aligned and successively positioned to provide a port-formed inlet conduit extending along the bottom of the contactor. In a like manner, thesuccessive outlet ports of the plates provide an outlet conduit along the top of the contactor.

Although such plate contactors can be scaled for greater capacity by adding additional plates, i.e., pas sageways, in parallel, it will be appreciated that the port sizes are fixed and therefore become a very practical limitation to the capacity achievable by the addition of more plates. Another practical limitation to the capacity available from a given number of plates is the small area available for flow into and out of the plate interspaces, that is, the passageways between the plates, from and to the inlet and outlet conduits formed by the successive ports of the plates.

Moreover, the throughput capacity of the contactor is in certain circumstances determined by the characteristics of the particular material to be stripped. For example, where the material is heat-sensitive, the capacity is often limited by the pressure drop across the contactor. On the other hand, when shear-sensitive materials are involved, the capacity is frequently limited by the flow velocity through the ports and into and out of the plate interspaces. It will be appreciated, therefore, that the cross-sectional flow area of the portformed inlet and outlet conduits, as well as the area available for flow to and from the plate interspaces, or passageways, may be determinative of the suitability of the contactor for stripping specific flowable materials. Since these physical characteristics of the contactor are fixed in the foregoing contactor, it is not possible, even when adding additional plates for greater capacity, to vary them so as to completely control pressure-velocity flow conditions within the contactor in correspondence with the sensitivities of the particular material being stripped.

These and other limitations of earlier plate contactors are overcome by the present invention.

SUMMARY OF THE INVENTION In accordance with the invention, a plate assembly constructed of a multiplicity of port-type liquid-liquid heat exchanger plates is gasketed so as to include in the confined tortuous path defined by the plates of the assembly an additional number of inlet ports, outlet ports, or both, to provide port-formed inlet and outlet conduits, and inlet and outlet areas between the respective conduits and the parallel passageways between the plates, of increased cross-sectional area, thus affording a plate assembly of increased capacity for a'given plate size. By varying the number of inlet or outlet ports included, it is possible to effect a corresponding variation of the cross-sectional flow area within the assembly and hence to control flow pressures and velocities along the tortuous path. Accordingly, not only may the capacity of the assembly be scaled still higher by adding additional plates, thus extending the range of utility of conventional liquid-liquid heat exchanger plates, but flow conditions within the assembly may be selectively controlled in correspondence with the particular sensitivities of the material to be treated.

The plate assembly, according to the invention, may be constructed of one or more sets of plates, with each set including a predetermined, although not necessarily equal, number of plates to define a predetermined number of elongate passageways. When more than one set is used, the outlet conduits of alternate sets in the series are positioned in face-to-face relationship with the inlet conduits of the next succeeding set of plates so that the material flowing through the assembly is intermittently changed in direction as it flows through the passageways defined by the respective sets of plates. By virtue of this intermittent changing of flow direction, together with high flow velocity, sufficient turbulence is created within the material flow to enhance transfer of the volatiles from the material.

Also, gasketing of the plates may be varied among the sets to provide the desired combination of inlet and outlet ports along the tortuous path. Normally the combination selected will depend upon the sensitivity of the flowable material to heat or flow velocity and will be such as to afford a maximum mass transfer of material without causing damage to the material, as might result, for example, from excessive pressure drops across the assembly or too high velocities in the ports or plate interspaces. It is contemplated, however, that the plates of at least one set will have two or more outlet ports included in the tortuous path, and that each succeeding set in the assembly will enlist at least a corresponding number of inlet and outlet ports in each plate, that is to say, each succeeding set will have at least two inlet conduits and two outlet conduits included in the flow path. The first set to include two outlet conduits need not, however, be the foremost set in the series, so that, if desired, the foremost set could enlist only a single inlet port and a single outlet port in each plate, and a succeeding set, such as the second set in the series, could be gasketed to form the two outlet conduits. Notwithstanding the foregoing, the foremost set of the assembly may be gasketed to provide two or more inlet or outlet conduits if considerations of flowable material quality require such an arrangement.

A plurality of sets of plates need not be used, of course, and similar advantages of increased flow capacity, extended utility of conventional heat exchanger plates, and improved flow characteristics are obtainable with a plate assembly having a single set of plates.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference may be made to the following description of an exemplary embodiment, taken in conjunction with the figures of the accompanying drawings, in which:

FIG. I is a schematic representation of a system for two-phase stripping of volatiles from a flowable material, illustrating a feed tank for the material to be stripped, an injector device for dispersing the flowable material in the form of discrete particles into a continuous phase gas or vapor flow, a plate contactor constructed according to the present invention, and a separator for separating the volatiles-containing vapor from the stripped material;

FIG. 2 is a diagrammatic view of one form of conventional liquiddiquid heat exchanger plate gasketed to include one inlet port and one outlet port in the flow path, and providing for diagonal flow of the stripping vapor and flowable material across the plate surface;

FIG. 3 is a diagrammatic view of the same form of heat exchanger plate shown in FIG. 2, showing a gasket arrangement enlisting all four ports in the plate to provide two inlet and two outlet ports in communication with the tortuous path;

FIG. 4 is a diagrammatic view generally similar to FIGS. 2 and 3, showing a gasketing arrangement ineluding a single inlet port and two outlet ports;

FIG. 5 is a diagrammatic view of another form of conventional liquid-liquid heat exchanger plate, depicting a gasketing arrangement enlisting three inlet ports and three outlet ports in the flow path;

FIG. 6 is an exploded view portraying a plurality of stripping plates arranged to provide a tortuous path for passage of the vapor-material admixture, showing dual-dual flow of the admixture between and through the plates;

FIG. 7 is a schematic illustration of a plate contactor including a series of sets of plates arranged in end-toend relation, showing representative paths traced by the vapor-material admixture as it flows through the contactor;

FIG. 8 is a diagrammatic view of the six-port heat exchanger plate of FIG. 5, as gasketed to provide for single-single port flow of a heating fluid through alternate passageways of the plate assembly; and

FIG. 9 also depicts a six-port plate, as gasketed to provide dual-dual port flow of the flowable material through alternate passageways.

DESCRIPTION OF A REPRESENTATIVE EMBODIMENT In the drawings, FIG. 1 illustrates the basic organization of a two-phase system for stripping volatiles from a flowable material in accordance with the novel process of US. Pat. No. 3,469,617 in the practice of which the plate assembly of the present invention has particular application. Essentially, the system includes a feed tank 10 for receiving a supply of flowable, volatilescontaining material through an inlet conduit 12 in an amount regulated by a control valve 14. A level control unit 16 is operatively connected between the tank 10 and the control valve 14 and functions to maintain the desired head of material in the tank 10 through appropriate regulation of the valve 14. A pump 18 located in a conduit 20 leading from the tank It) delivers the material to an injection device 22 connected in the inlet conduit 24 for the stripping vapor, the device 22 functioning to disperse the flowable material as discrete particles in the stripping vapor flow so as to produce a homogeneous admixture having a continuous vapor phase and a discontinuous material phase.

Thereafter, the admixture of volatiles-containing material and stripping vapor is passed through a plate assembly 26, here in the form ofa plate contactor, which presents a confined, tortuous path to the admixture flow, and in which the particles of flowable material are brought into intimate volatiles-transferring contact with the stripping vapor to effect stripping of the volatiles from the material. After passage through the contactor 26, the stripping vapor, now containing the volatiles, and the stripped material particles are passed through a connecting conduit 28 to a separator 30 where physical separation of the stripping vapor and volatiles from the material residue is carried out. Conveniently, the vaporous elements of the admixture are exhausted through a conduit 32 at the top of the separator and are passed to a condenser for recovery. The stripped material residue, on the other hand, may be drawn off through a conduit 34 at the bottom of the separator 30 for further processing, if required, or for delivery to one or more successive stripping stages for more complete removal of volatiles from the material.

The conditions under which the flowable material is injected into the vapor flow are, of course, carefully controlled to afford optimum entrainment and dispersion of the flowable material throughout the stripping vapor flow, while fully' preserving the material against damage as a result of its being exposed to the stripping vapor. These conditions, as well as various types of devices which have been found to be suitable for injecting the flowable material into the stripping vapor, are considered in detail in U.S. Pat. No. 3,469,617, most particularly at lines 71 to 75 of column 3 and lines I to 70 of column 4, and accordingly, are not repeated here. The referenced passages are, however, hereby incorporated into the present specification. Similarly, the types of flowable materials and stripping vapors, or gases, suitable for treatment and use in the foregoing system are fully described in that patent, principally at lines 71 to 75 column 4 and lines 1 to 45 of column 5, this material also being incorporated here by reference.

As is furtherdescribed and illustrated in the aforementioned patent, the plate contactor 26 is constructed of one or more sets of port-type heat exchanger plates of conventional design arranged in succession, with the individual plates being separated by gaskets and retained in assembled relation by a suitable clamping structure 35. A series of elongated parallel passageways is thereby defined extending lengthwise of the plates in a direction lateral to the flow of the vapor and material admixture. With this arrangement, the contactor provides a confined, tortuous path in which intimate turbulent contacting of the flowable material and stripping vapor is readily and thoroughly effected.

FIG. 2 illustrates, in diagrammatic form, a liquidliquid heat exchanger plate 36 of conventional fourport design, and demonstrates the single-single gasketing arrangement commonly used with such plates ina liquid-liquid heat exchanger and that, heretofore, has been used as well in the plate contactor of U.S. Pat. No. 3,469,617. As indicated by the stippling of the plate surface, the plate is gasketed to enlist a single inlet port 38a adjacent one lower comer of the plate and a single outlet port 40b at the diagonally opposite upper end of the plate and to enclose with the adjacent plates a narrow, elongate passageway extending across the surface of the plates between the inlet port 38a and the outlet port 40b. The stripping vapor-material admixture enters through the port 38a, flows generally in the direction of the arrows across the plate to the outlet port 40b. Inasmuch as conventional heat exchanger plates of this type normally have roughened surfaces, the flow between the inlet and outlet ports is turbulent, with frequent collisions occurring between the particulate flowable material and the plate surfaces, to the end that the particles are further fragmented, hence bringing new material surfaces into contact with the stripping vapor and accelerating the removal of the volatiles.

The remaining inlet and outlet ports of the plates, for example, ports 38b and 40a of the plate 36 are not used, but typically are provided with ring gaskets 42 for proper plate support and for closing of the ports.

In certain applications of the plate assembly, however, a heating fluid may be circulated through the plate ports not enlisted in the tortuous path and, if so, the ring gaskets 42 are used to seal against loss of heating medium. This, for example, is the case in the plate evaporator type of plate assembly disclosed in U.S. Pat.

No. 3,073,380 (see in particular FIGS. 2 and 4), issued Jan. 15, 1963 to the assignee of this application.

In addition, generally U-shaped recesses 44 typically are provided in the heat exchanger plate 36 to receive elongate supporting rods (not shown) to hold the plates in proper assembled relation.

Although a plate contactor constructed in accordance with the foregoing and gasketed as illustrated in FIG. 2, affords good two-phase dispersed flow contactingof the stripping vapor and the flowable material, and accordingly provides efficient stripping of volatiles from the flowable material, it is subject to the abovedescribed limitations in respect of capacity and adaptability to the particular material being conveyed through the contactor. Notwithstanding this, it will be understood that the gasketing arrangement of FIG. 2 may be used to advantage in certain applications; indeed, as is more fully described hereinafter, it is a feature of the present invention that the single-single gasket configuration of FIG. 2 is usable in combination with other gasket configurations to allow desired regulation of flow conditions along the tortuous path.

As mentioned, this invention overcomes the limitations associated with the earlier forms of plate contactor by enlisting one or more inlet ports, outlet ports, or both, in each plate in communication with the tortuous flow path, thereby increasing the cross-sectional flow area of port-formed conduits and of the flow areas leading from the inlet conduits to the plateinterspaces and from the plate interspaces to the outlet conduits. It is also contemplated that various gasketing configurations may be used within the contactor so as to vary the cross-sectional flow area provided in a way to create the desired flow conditions along the tortuous path.

Therefore, there are illustrated in FIGS. 3, 4 and 5, three representative gasketing configurations that may be used in accordance with the invention. In FIG. 3, for example, a conventional four-port heat exchanger plate 46 is shown gasketed to include both inlet ports 48a and 48b and both outlet ports 50a and 50b in communication with the elongate passageway extending across the plate surface (the stippling indicates the plate surface area enclosed by the gasket). With this arrangement, referred to hereinafter as the dual-dual arrangement, it will be appreciated that flow of the stripping vapor-material admixture is admitted to the passageway through both of the inlet ports 48a and 48b and is exited from the passageway through the two outlet ports 50a and 50b (see the arrows in FIG. 3), and that this will result in a doubling of the cross-sectional flow area of the ports and of the areas connecting the respective ports with the passageway as compared to the configuration of FIG. 2. Clearly, therefore, a plate contactor gasketed as illustrated in FIG. 3 would have twice the ultimate vapor flow capacity of a contactor gasketed according to FIG. 2, or, conversely, would at the same vapor rate reduce the velocity of flow of the admixture along the tortuous path by one-half. Intermediate throughputs and velocities are of course obtainable by appropriate regulation of the input to the plate contactor.

With the dual-dual configuration of FIG. 3, significantly higher vapor capacities are possible for a given pressure drop along the tortuous path as compared to the single-single configuration of FIG. 2. This is a particularly advantageous feature in the stripping of heat sensitive materials, for example, inasmuch as it permits high input volumes and velocities to be maintained while avoiding an excessive, corresponding increase in the temperature of the stripping vapor owing to a high pressure drop across the contactor.

Another gasketing arrangement according to the invention is depicted in FIG. 4, where one inlet port 58a and two outlet ports 60a and 60b of a four-port, liquidliquid heat exchanger plate 56 are shown included in communication with the tortuous flow path. As illustrated by the arrows, the flow in this case would be through the single inlet port 58a, across the surface of the plate 56 and through the outlet ports 60a and 60b. While affording a throughput capacity less than the arrangement of FIG. 3, the single-dual gasketing arrangement of FIG. 4 provides increased capacity as compared to the arrangement of FIG. 2. Desirably, a ring gasket 62 is provided around the unused inlet port 58b to afford proper support for the plate 56 and to seal against loss of heating fluid if it is used.

Still another possible gasketing arrangement is shown in FIG. 5, this time witha conventional liquid-liquid heat exchanger plate 66 having three inlet ports 68a, 68b, and 68c, and three outlet ports 70a, 70b, and 700,

enclosed in communication with the passageway defined by the gasket across the plate surface (see the stippling in FIG. 5). It will be appreciated, of course, that by enlisting three inlet ports and three outlet ports in the tortuous flow path, the total capacity of the plate contactor can be still further increased, or the flow velocity still further reduced, to meet the requirements of a given application. Furthermore, not all three of the inlet or outlet ports need be enclosed by the gasket. For example, one inlet port could be gasketed in communication with two or three outlet ports or two inlet ports could be combined with two or three outlet ports depending upon the particular flow conditions desired.

With particular reference to FIG. 6, the manner of flow of the stripping vapor-material admixture through a plate contactor constructed in accordance with the invention is illustrated in connection with the-dualdual" gasketing configuration of FIG. 3. A multiplicity of port-type heat exchanger plates, say, for example, plates 72, 74, 76, 78, and 80, are arranged in succession to form a single set and are adapted to be maintained-in close spaced relation by gaskets (not shown) interposed between adjacent plates so as to define a predetermined number of elongate, narrow passageways (indicated by the stippling in FIG. 6) extending laterally of the direction of flow to the contactor.

In the arrangement shown, the foremost plate 72 is provided with two inlet ports 72a and 72b for receiving the fiow of stripping vapor and flowable material from the injection device 22 (see FIG. 1). For this purpose, the conduit 24 leading to the contactor 26 is conveniently split in two downstream of the injection device 22 so as to deliver the vapor-material admixture to the plate 72 in two equal streams (as indicated by thearrows in FIG. 6). Suitably the plate 72 is a feeder-type plate and therefore will not have outlet ports adjacent its upper end.

As illustrated in FIG. 6, where the plate sequence is shown interrupted for clarity, the admixture passes through the inlet ports 72a and 72b of the plate 72, with the main portions of the two inlet streams thereafter flowing through inlet conduits" 82a and 82b, respectively, formed by the successively positioned inlet ports 74a, 76a, and 78a and ports 74b, 76b, and 78b, respectively, while lesser amounts of the admixture are successively passed laterally through the elongate passageways between the plates as a plurality of individual turbulent streams. The flowable material is thus brought into intimate contact with the stripping vapor and the transfer of the volatiles contained by the material to the vapor is effected. Upon reaching the upper end of the plate, the turbulent streams exit from the parallel passageways and enter the outlet conduits 84c and 84d formed by the successively arranged outlet ports 74c, 76c, 78c, and 800 and 74d, 76d, 78d, and d, respectively. After passing through the outlet ports 80c and 80d of the last plate of the series, the admixture of the stripped flowable material and the volatiles-containing vapor may be directed to a separator, such as that indicated as 30 in FIG. 1, for separation of the vaporous constituent elements from the material residue, or it may be received in a successive set or sets of plates, defining additional confined passageways, for further stripping of the volatiles from the flowable material.

Also, if desired, the foremost plate 72 of the set represented in FIG. 6 could be gasketed or formed to include only one inlet port. This would simplify the piping leading to the contactor and, in addition, would maintain a more uniform flow velocity through the contactor. It will be understood as well that the plates 72, 74, 76 and 78 could be gasketed in accordance with the configuration of FIGS. 2 or 4, or could take the form and have the gasket arrangement of FIG. 5.

FIG. 7 illustrates schematically a contactor having a number of passes, i.e., sets of plates, arranged in series for successively receiving flow of the vapor-material admixture. Three passes or sets 86, 88, and are shown and, as described more fully hereinafter, any one or a combination of the gasketing configurations of FIGS. 2 to 5 may be employed among the sets.

As is clear from FIG. 7, (assuming for convenience of description that all sets are gasketed for dual-dual flow) the sets are assembled in end-to-end relation such that the outlet conduits 86b of the first set 86 of plates are positioned face-to-face with the inlet conduits 88a of the set 88 which next succeeds the set 86. The outlet conduits 88b of the set 88 are also in face-to-face relationship with the inlet conduits 90a of the next succeeding set 90, and so-forth until the last set of the contactor. The vapor-material admixture is therefore inter mittently changed in direction as it flows through the passageways defined by the respective sets of plates in the manner indicated by the arrows in FIG. 7. Advantageously, this intermittent changing of direction, together with high flow velocity, creates sufficient turbulence within the material and stripping vapor flow so that particles of the flowable material are continuously brought into contact with the confining walls or surfaces of the plates with the result that volatilestransferring contact between the material and the vapor is enhanced. It will be appreciated that sufficient sets of plates, or passes, are provided in the contactor to effect the desired stripping of the volatiles from the material.

In the last set of plates, for example, set 90 of FIG. 7, the material enters through the inlet conduits 90a and is deflected upwardly through the lateral passageways to the outlet conduits 9012 where it exits from the contactor through the outlet ports of the last plate. Thereafter, the stripped material and volatilescontaining vapor are delivered to the separator 30 (see FIG. 1) or are received in a succeeding stripping stage for further removal of the volatiles from the material. One possible arrangement of a further stripping stage is depicted in FIG. 6 of U.S. Pat. No. 3,469,617.

As mentioned, it is an important aspect of the invention that the gasketing of the plates may be varied among the sets of the contactor. That is to say, although all of the plates may be gasketed alike, for example, as in FIG. 3 to provide for dual-dual flow throughout the contactor, one or more of the sets may be provided with a different gasketing configuration. Thus, set 86, (see FIG. 7) could be provided with the single-dual configuration of FIG. 4, and each of the succeeding sets 88 and 90 could have the dual-dual gasketing arrangement of FIG. 3. Alternatively, set 86 could be provided with the single-single gasketing configuration of FIG. 2, with set 88 then having a single-dual gasketing arrangement and the succeeding sets 90, etc., having the dual-dual arrangement. It is contemplated, therefore, that any combination of gasketing arrangements might be used along the length of the flow path in order to obtain optimum flow conditions for the particular material being stripped. Each succeeding set of the contactor, however, will normally have the same number of inlet conduits as the next preceding set has outlet conduits so that the flow through the contactor will not be restricted.

By varying the gasketing of the plates, thereby varying the number of inlet and outlet ports enlisted, it is possible to effect a corresponding variation of the cross-sectional flow area within the contactor and hence to control flow pressures and velocities along the tortuous path. In this way flow conditions within the contactor may be optimized in correspondence with the sensitivities of the material being stripped to allow high throughput capacities while preserving the material against damage.

Accordingly, when stripping shear-sensitive materials, for example, theforemost plate of the first set, or perhaps even each plate of the first set, might be provided with the single-dual" gasketing arrangement (see FIG. 4) and the following sets may be provided with the dual-dual" gasketing arrangement (see FIG. 3). This porting sequence allows a high feed pressure with correspondingly lower throughput volumes and velocities, and thus permits good mass transfer of material through the contactor without unduly increasing flow velocity. On the other hand, if a temperaturesensitive material is being stripped, all of the sets in the contactor could be gasketed to provide "dual-dual" flow. Here, the overall flow pressure drop must be kept low to reduce the feed pressure and temperature and thus high feed volume must be accommodated. The dual-dual" gasket configuration has been found to be particularly useful for this purpose.

It should also be noted that the use of specially designed large port plates has been considered as a possible solution to the handling of shear-sensitive materials. However, it is of particular importance that the construction of the plate assembly of this invention allows extension of the range of applicability of available standard corner port-type heat exchanger plates, and thereby eliminates the need for costly experimentation and fabrication of other suitable plate designs.

The operation and results obtained by use of the plate assembly of this invention are further illustrated in the following examples:

EXAMPLE I In order to demonstrate the advantages obtained by using the plate assembly of the present invention as compared to the use of a contactor constructed to provide single-single port flow, two runs, each involving three separate passages of the flowable material through the contactor, were carried out in a system of the type illustrated in FIG -1n the first run, size 01 Rosenblads conventional porttype plates were provided with asbestos gaskets to provide a single inlet and outlet flow as illustrated in FIG. 2. These plates were arranged 101010-l0l0, (i.e., in parallel sets of 10 plates each, arranged in series to provide a five pass plate stripping unit). In the second run, the same size plates were gasketed for dual-dual flow as illustrated in FIG. 3 and were arranged 9999-9, (i.e., in sets of 9 parallel plates each, arranged in series to provide a 5 pass plate stripping unit).

A carboxylated styrene-butadiene latex containing approximately 3 percent styrene monomer at a total solids content of from 41 to 42 percent was then stripped in three passages in the stripping systems utilizing the two different plate contactors. Both runs were conducted for 6.5 hours duration. Since pH is a particularly critical variable in the stability of this type of acid latex, during stripping the pH was held essentially constant during the two runs by adding ammonia (as ammonium hydroxide) between successive passages through each of the contactors to keep the product pH at 8.0 or higher. As shown in the following tabulation of data, in the firstrun using the single inlet and single outlet port plates, light dusting," i.e., deposition, of the latex material occurred on the plate surfaces; whereas in the second run, using dual-dual flow, all plates were clean. No foaming occurred in either run.

Run No. 1

(Start latex: 3.2% styrene, 41.3% T.S., pH 9.3)

Average Rates & Conditions lst 2nd 3rd Passage Passage Passage Latex, lbs/hr 540 540 540 Steam, lbs/hr 190 215 220 Inlet Tempi, F. 200 202 202 Product p 8.0 8.1 8.1 Product. Wt.%

Styrene, at 50%T.S. 0.90% 0.24% 0.06% Plates Condition: Light "dusting" on plates. Few chunks of coagulum.

Run No. 2

(Start latex: 2.9% styrene, 42.0% T.S., pH 9.3)

Average Rates & Conditions lst 2nd 3rd Passa e Passage Passa e Latex, lbs/hr 4 0 590 550 Steam, lbs/hr 207 210 Inlet Temp., F. 206 208 209 Product pH 8.0 8.3 8.3 Product, Wt.% Styrene, at 50% T.S. 0.73% 0.l7% 0.05%

Plates Condition: All plates clean.

It will be recognized that the percent narrower plate arrangement employed in Run No. 2 and the higher initial mixing temperature both provide a more severe test of the dual-dual flow gasketed contactor. Nevertheless, it is clearly demonstrated from the above data that shear-induced latex destabilization is reduced to an undetectable level, if not eliminated altogether, in Run No. 2 by doubling the flow area of the ports. In contrast, in Run No. 1, light dusting occurred throughout most of the plates and chunks of coagulum appeared on the first plates of the second and fifth passes.

It will also be noted from the above data that the conditions used in both of the runs were such that the level of stripping in both runs was the same, thus further indicating the improvement provided by the subject invention.

EXAMPLE ll Utilizing the same type of dual-dual plates used in Run No. 2 of Example l, a commerical three stage stripping apparatus was scaled up using stages of the type shown in FIG. 1 for the same type of carboxylated styrene-butadiene latex utilizing 4,033 pounds per hour of steam flow. In this case, two 5-inch diameter ports at each end of the plates were combined to obtain capacities heretofore not practicable with the available plate. Also it was again found that no deposition of latex material occurred on the plate surfaces.

It will be recognized that the above data further show that the plate contactor of this invention will also find utility in cases other than stripping of shear-sensitive latices. Thus, this invention provides a stripping technique for increasing the flow capacity of a given plate size in that the area between the plates can be considerably increased by simply adding plates in parallel up to a point where the greater port area becomes limiting. As mentioned above, the invention may be advantageously applied to plate evaporators such as those described in US. Pat. No. 3,073,380 in which a heating fluid and the flowable material are passed through alternate passageways between the plates. Those portions of that patent which pertain to the construction and operation of plate evaporators, and as depicted in FIGS. 2 and 4 in particular, are hereby incorporated into this specification. Advantages over prior art evap orators similar to those realized overprior art plate contactors are therefore obtainable.

By way of further illustration of a plate evaporator constructed according to the invention, reference is made to FIGS. 8 and 9. FIG. 8 represents a plate gaskcted for single-single" port flow of heating fluid and FIG. 9 portrays "dual-dual port flow of flowable material. ln FIG. 8, therefore, one inlet port and one outlet port (e.g., the center ports 92b and 94b) of the three inlet ports 92a, 92b and 920 and three outlet ports 94a, 94b, and 940, respectively, of the plate 106 are included in communication with the passageway between the plates. (As before the stippled area lies within the gasket.) A ring gasket 96 seals off inlet ports 92a and 92c and outlet ports Qa and Me so as to enclose those ports in the confined tortuous path for the flowable material, thus transmitting the material through the plate 106 to the next passageway. That passageway is coupled at one end to the inlet ports 92a and 92c and at the other to the outlet ports 94a and 940 by a suitably shaped gasket. (Again, the stippling indicates the enclosed plate area.) Middle ports 92b and 94b are encircled by ring gaskets 98, thereby including them in the flow path for the heating fluid. Thus it will be appreciated that alternate passageways are included in the confined tortuous path for the flowable material, on the one hand, and in a confined flow path for the heating fluid, on the other.

Of course, instead of two inlet ports 92a and 92c for the flowable material, only one could be used. This would then give single-single port flow for the heating medium and single-dual port flow for the flowable material.

US. Pat. No. 3,073,380 makes reference to flash" as well as open evaporation systems, and indicates that the process and apparatus there described have application to both types of systems. The present invention, therefore, is likewise applicable to both, including, for example, the use of all of the passageways between the plates of one or more sets of the assembly to achieve flashing (evaporation) flow let-down of previously heated flowable material.

Those skilled in the art will understand that the foregoing embodiments of the plate assembly are merely exemplary, in that they are susceptible of modification and variation without departing from the spirit and scope of the invention. All such variations and modifications therefore, are intended to be included within the scope of the appended claims.

I claim:

1. A plate assembly providing a confined tortuous path for two-phase stripping of volatiles from a flowable material comprising:

a plurality of standard generally rectangular porttype heat exchanger plates successively arranged in closely spaced, parallel relation so as to provide therebetween a plurality of parallel passageways;

the foremost plate and each interior plate having an inlet port in each corner at one end thereof and the last plate and each interior plate having an outlet port in each corner at the other end thereof;

gasket means interposed between successive adjacent plates for enclosing in the confined tortuous path (1) at least one inlet port of the foremost and each interior plate, (2) both outlet ports of the last and each interior plate, and (3) each of said parallel passageways, said enclosed passageways being in flow communication with said enclosed inlet and outlet ports of the plates; and

means for holding the plates and gasket means in assembled relation such that the inlet ports are in generally coaxial alignment and the outlet ports of the plates are likewise in generally coaxial alignment, the successive enclosed inlet ports thereby forming as many inlet conduits as there are enclosed inlet ports in each of the respective plates and the successive enclosed outlet ports thereby forming two outlet conduits, the inlet and outlet conduits extending in a direction generally transverse to the passageways between the plates and communicating with said enclosed passageways, whereby a two-phase mixture of a stripping gas and a flowable material containing volatiles to be removed introduced through an inlet conduit is first passed through all said enclosed passageways to enhance release of the volatiles from the material and is thereafter discharged through the two outlet conduits. v

2. A plate assembly according to claim 1 in which:

said gasket means encloses both inlet ports of the foremost and each interior plate in the confined tortuous path, thereby forming two inlet conduits so as to afford dual-dual port flow of the stripping gas-flowable material mixture through the plates.

3. A plate assembly according to claim 1 in which said gasket means comprises a continuous elongate gasket interposed between each pair of plates forming said enclosed passageways, the gasket extending in part along the peripheries of the pair of plates and enclosing said enclosed inlet and outlet ports thereof.

4. A plate assembly according to claim 1 in which:

the foremost plate and each interior plate have a third inlet port intermediate to said corner inlet ports, and the last plate and each interior plate have a third outlet port intermediate to said corner outlet ports; and

said gasket means also encloses in the confined tortuous path said third outlet port.

5. A plate assembly according to claim 4 in which said gasket means encloses at least one additional inlet port of the foremost and each interior plate in said confined tortuous path, thereby forming at least two inlet conduits and three outlet conduits so as to afford dualtriple port flow through the plates.

6. A plate assembly providing a confined tortuous path for two-phase stripping of volatiles from a flowable material comprising:

a plurality of sets of standard generally rectangular port-type heat exchanger plates, the sets being assembled in an end-to-end series, with each set including a predetermined number of plates successively. arranged in closely spaced parallel relation so as to provide therebetween a plurality of parallel passageways;

the foremost plate and each interior plate of each set having an inlet port in each corner at one end thereof and the last plate and each interior plate of each set having an outlet port in each cornerat the other end thereof;

gasket means in one set interposed between successive adjacent plates for enclosing in the confined tortuous path (1) at least one inlet port of the foremost and each interior plate, and both outlet ports in the last and each interior plate, gasket means in each set preceding said one set in the series for enclosing in the confined tortuous path as many inlet ports in the foremost and each interior plate and as many outlet ports in the last and each interior plate as there are enclosed inlet ports in said one set, gasket means in each set following said one set in the series for enclosing in the confined tortuous path as many inlet ports in the foremost and each interior plate and as many outlet ports in the last and each interior plate of each following set, as there are outlet ports in the last and each interior plate of said one set and, said gasket means in each set enclosing each of said parallel passageways between the plates of the sets in flow communication with said enclosed inlet and outlet ports of the plates; and

means for holding the plates of the sets and the gasket means in assembled relation such that l) the inlet ports of the plates are in generally coxial alignment and outlet ports of the plates are likewise in generally coaxial alignment, the successive enclosed inlet ports of each set thereby forming as many inlet conduits as there are enclosed inlet ports in the plates of the set and the successive enclosed outlet ports thereby forming as many outlet conduits as there are enclosed outlet ports in the plates of the set, said inlet and outlet conduits extending in a direction generally transverse to the passageways between the plates and communicating with said enclosed passageways, and such that (2) each inlet conduit of each succeeding set is aligned with an outlet conduit of the next preceding set, whereby a two-phase mixture of a stripping gas and a flowable material containing volatiles to be removed introduced into the inlet conduitor conduits of the foremost set is sequentially passed through said enclosed parallel passageways of the foremost set, the outlet conduit or conduits of the foremost set, and the inlet conduits, enclosed inlet ports, enclosed passageways, enclosed outlet ports and outlet conduits of each succeeding set thereby to enhance release of thevolatiles from the material.

7. A plate assembly according to claim 6 in which said one set is the last set in the series.

8. A plate assembly according to claim 6 in which:

the foremost and each interior plate of each set have a third inlet port intermediate to said corner inlet ports and the last plate and .each interior plate of each set have a third outlet port intermediate to said corner outlet ports; and

said gasket means encloses at least two of the inlet ports of the foremost and each interior plate of said one set and all of the outlet ports of the last and each interior plate of said one set;

9. A plate assembly according to claim 6 in which said gasket means encloses both inlet ports of the foremost plate and each interior plate of each set, so as to afford dual-dual port flow through all sets of plates.

10. A plate assembly according to claim 9 in which said gasket means comprises a continuous elongate gasket interposed between each pair of plates forming said enclosed passageways, the gasket extending in part along the peripheries of the pair of plates and enclosing said enclosed inlet and outlet ports thereof.

t i k "H050 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3,759,308 Dated September 18) 1973 Inventofls) Adam George Gebauer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5', line '29, "75 column" should read -75 of column- Column '14, line 1, "there are" should read --there are enclosed*--;

' line 10, "coxial" should be --coaxial--;

'line' '47 semi-colon should be a period.

Signed and sealed this 9th day of April 197b,.

(SEAL) Attest:

C. MARSHALL DANN Commissioner of Patents EDWAFD I LFLETCHERJR. Attesting Officer 

1. A plate assembly providing a confined tortuous path for twophase stripping of volatiles from a flowable material comprising: a plurality of standard generally rectangular port-type heat exchanger plates successively arranged in closely spaced, parallel relation so as to provide therebetween a plurality of parallel passageways; the foremost plate and each interior plate having an inlet port in each corner at one end thereof and the last plate and each interior plate having an outlet port in each corner at the other end thereof; gasket means interposed between successive adjacent plates for enclosing in the confined tortuous path (1) at least one inlet port of the foremost and each interior plate, (2) both outlet ports of the last and each interior plate, and (3) each of said parallel passageways, said enclosed passageways being in flow communication with said enclosed inlet and outlet ports of The plates; and means for holding the plates and gasket means in assembled relation such that the inlet ports are in generally coaxial alignment and the outlet ports of the plates are likewise in generally coaxial alignment, the successive enclosed inlet ports thereby forming as many inlet conduits as there are enclosed inlet ports in each of the respective plates and the successive enclosed outlet ports thereby forming two outlet conduits, the inlet and outlet conduits extending in a direction generally transverse to the passageways between the plates and communicating with said enclosed passageways, whereby a two-phase mixture of a stripping gas and a flowable material containing volatiles to be removed introduced through an inlet conduit is first passed through all said enclosed passageways to enhance release of the volatiles from the material and is thereafter discharged through the two outlet conduits.
 2. A plate assembly according to claim 1 in which: said gasket means encloses both inlet ports of the foremost and each interior plate in the confined tortuous path, thereby forming two inlet conduits so as to afford dual-dual port flow of the stripping gas-flowable material mixture through the plates.
 3. A plate assembly according to claim 1 in which said gasket means comprises a continuous elongate gasket interposed between each pair of plates forming said enclosed passageways, the gasket extending in part along the peripheries of the pair of plates and enclosing said enclosed inlet and outlet ports thereof.
 4. A plate assembly according to claim 1 in which: the foremost plate and each interior plate have a third inlet port intermediate to said corner inlet ports, and the last plate and each interior plate have a third outlet port intermediate to said corner outlet ports; and said gasket means also encloses in the confined tortuous path said third outlet port.
 5. A plate assembly according to claim 4 in which said gasket means encloses at least one additional inlet port of the foremost and each interior plate in said confined tortuous path, thereby forming at least two inlet conduits and three outlet conduits so as to afford dual-triple port flow through the plates.
 6. A plate assembly providing a confined tortuous path for two-phase stripping of volatiles from a flowable material comprising: a plurality of sets of standard generally rectangular port-type heat exchanger plates, the sets being assembled in an end-to-end series, with each set including a predetermined number of plates successively arranged in closely spaced parallel relation so as to provide therebetween a plurality of parallel passageways; the foremost plate and each interior plate of each set having an inlet port in each corner at one end thereof and the last plate and each interior plate of each set having an outlet port in each corner at the other end thereof; gasket means in one set interposed between successive adjacent plates for enclosing in the confined tortuous path (1) at least one inlet port of the foremost and each interior plate, and both outlet ports in the last and each interior plate, gasket means in each set preceding said one set in the series for enclosing in the confined tortuous path as many inlet ports in the foremost and each interior plate and as many outlet ports in the last and each interior plate as there are enclosed inlet ports in said one set, gasket means in each set following said one set in the series for enclosing in the confined tortuous path as many inlet ports in the foremost and each interior plate and as many outlet ports in the last and each interior plate of each following set, as there are outlet ports in the last and each interior plate of said one set and, said gasket means in each set enclosing each of said parallel passageways between the plates of the sets in flow communication with said enclosed inlet and outlet ports of the plates; and means for holding the plates of the sets and the gasket meanS in assembled relation such that (1) the inlet ports of the plates are in generally coxial alignment and outlet ports of the plates are likewise in generally coaxial alignment, the successive enclosed inlet ports of each set thereby forming as many inlet conduits as there are enclosed inlet ports in the plates of the set and the successive enclosed outlet ports thereby forming as many outlet conduits as there are enclosed outlet ports in the plates of the set, said inlet and outlet conduits extending in a direction generally transverse to the passageways between the plates and communicating with said enclosed passageways, and such that (2) each inlet conduit of each succeeding set is aligned with an outlet conduit of the next preceding set, whereby a two-phase mixture of a stripping gas and a flowable material containing volatiles to be removed introduced into the inlet conduit or conduits of the foremost set is sequentially passed through said enclosed parallel passageways of the foremost set, the outlet conduit or conduits of the foremost set, and the inlet conduits, enclosed inlet ports, enclosed passageways, enclosed outlet ports and outlet conduits of each succeeding set thereby to enhance release of the volatiles from the material.
 7. A plate assembly according to claim 6 in which said one set is the last set in the series.
 8. A plate assembly according to claim 6 in which: the foremost and each interior plate of each set have a third inlet port intermediate to said corner inlet ports and the last plate and each interior plate of each set have a third outlet port intermediate to said corner outlet ports; and said gasket means encloses at least two of the inlet ports of the foremost and each interior plate of said one set and all of the outlet ports of the last and each interior plate of said one set;
 9. A plate assembly according to claim 6 in which said gasket means encloses both inlet ports of the foremost plate and each interior plate of each set, so as to afford dual-dual port flow through all sets of plates.
 10. A plate assembly according to claim 9 in which said gasket means comprises a continuous elongate gasket interposed between each pair of plates forming said enclosed passageways, the gasket extending in part along the peripheries of the pair of plates and enclosing said enclosed inlet and outlet ports thereof. 